1. Field of the Invention
The present invention generally relates to a technology for using geothermal water in an aquifer as a heating and cooling medium for exchanging the heat, and more particularly to a double-pipe geothermal water circulating apparatus that can circulate said geothermal water by returning used geothermal water to said aquifer or an above-located aquifer for exchanging the heat.
2. Description of the Related Art
It is generally known that the underground temperature is lower and higher than the outer temperature in summer and winter, respectively and the geothermal temperature becomes high as its observed point comes deeper. In a conventional invention, by pumping underground geothermal water in an aquifer, the geothermal water is used as a cooling medium in summer and a heating medium in winter.
FIG. 7 shows a conventional type of heat exchanging system using geothermal water. In the heat exchanging system 700, a water collecting tank 710 is installed underground as deep as an aquifer A to feed the geothermal water collected in the water collecting tank 710 to an heat exchanger 750 using a pump 730. Then, used geothermal water is transported to a sewage treatment facility 780 to treat waste water and to an underground geothermal water returning well 770 to be reused underground. In fact, such an heat exchanging system can directly feed the geothermal water to the heat exchanger 750, thereby relatively reducing thermal energy loss and improving thermal efficiency.
Despite these technological advantages, the conventional type of heat exchanging system 700, as shown in FIG. 7, has a drawback of higher initial costs due to required construction of the sewage treatment facility 780 for treating the used geothermal water and the geothermal water returning well 770. Also, this system, which is not designed to return the collected geothermal water to the aquifer A, could cause serious environmental concerns such as exhaustion of water in a well and ground subsidence due to excessive water intake. Consequently, this system is not actually used in most heat exchanging operations.
In the meantime, this inventor proposed an underground geothermal water circulating apparatus that can efficiently melt snow by solving the above-mentioned problems as disclosed in the Japanese Unexamined Patent Publication No. 06-228928.
FIG. 8 is a block diagram showing a first embodiment of the underground geothermal water circulating apparatus according to claim 1 of said Japanese Unexamined Patent Publication. An underground geothermal water circulating apparatus 800 comprises a cylinder-type geothermal source collecting casing 810 filled with a medium liquid installed underground, a cylinder-type thermal insulating casing 820 at the axial core of the geothermal source collecting casing 810 and a pump 830 in the thermal insulating casing 820. Then, said pump 830 sucks said medium liquid and distributes it to a non-water spray type snow melting system 850 as a snow-melting heat source. After used medium liquid of a lower temperature is returned to the geothermal source collecting casing 810, it is heated by geothermal source via a side wall of said geothermal source collecting casing 810. Afterward, the pump 830 sucks said medium liquid into said thermal insulating casing 820 and it is repeatedly used as a snow-melting heat source.
FIG. 9 is a block diagram showing a second embodiment of the underground geothermal water circulating apparatus according to claim 2 of said Japanese Unexamined Patent Publication. An underground geothermal water circulating apparatus 900 comprises a cylinder-type geothermal source collecting casing 910 installed underground having a geothermal liquid collecting strainer 911 for collecting geothermal water from an aquifer and a snow-melted water reusing liquid returning strainer 912 placed above said geothermal liquid collecting strainer 911 for returning geothermal water used in a snow melting system 950 to an underground zone. Said geothermal source collecting casing 910 is provided with a cylinder-type thermal insulating casing 920 at the axial center thereof. A separating packer 990 is mounted on a wall between said geothermal source collecting casing 910 and said thermal insulating casing 920 for separating reused and collected geothermal liquids.
In the underground geothermal water circulating apparatus 900 of the second embodiment as described above, the geothermal liquid collecting strainer 911 collects the geothermal water to the geothermal source collecting casing 910, which will be sucked by the pump 930 to said thermal insulating casing 920 and then the snow melting system 950. Afterward, geothermal water used in the snow melting system 950 returns to the geothermal source collecting casing 910 as a reused geothermal liquid and it is discharged from the snow-melted water reusing liquid returning strainer 912 and reused in the aquifer. The separating packer 990 can prevent the mixture of the reused and collected geothermal liquids.
The underground geothermal water circulating apparatus disclosed in the above Japanese Unexamined Patent Publication is expected to provide several technological advantages, such as lower installation costs in one integrated unit, a small rate of mechanical failure due to simplified structure and no exhaustion of water in a well and ground subsidence due to excessive water intake by reusing the medium and geothermal liquids.